Crescentic Fibrillary Glomerulopathy

Fibrillary glomerulopathy is a rare disorder of unknown etiology and pathophysiology, which is characterized by deposition of course, randomly-oriented, non-branching fibrils within the mesangium and/or capillary loops. These deposits typically show positive “smudgy” glomerular staining for IgG, C3, kappa and lambda by immunofluorescence. The pattern of glomerular injury by light microscopy is variable; however, mesangial matrix expansion by a PAS-pale, weakly argyrophilic material is almost always present. Cellular crescents (Fig 1 and 2), although uncommon, have been described in up to 17% of cases (see reference). Given the rarity of this pattern of glomerular injury, its clinical significance is still to be determined. Excluding other causes of crescentic glomerulonephritis is required prior to establishing the diagnosis of crescentic fibrillary glomerulopathy.